This proposal will support the research and further the applicant's training as a clinician-scientist at the nexus of psychiatry and sleep disorders medicine. Dr. Plante's goals are to examine the neurophysiology of hypersomnolence in depression during sleep and wakefulness, to identify biomarkers for excessive sleepiness, and to ultimately translate these findings into targeted neuromodulatory interventions for individuals with mood disorders. To achieve these aims, a didactic plan focused on the development of: 1) a stronger conceptual grounding of advanced high-density electroencephalogram (hdEEG) applications in mood and sleep disorders research, and 2) more sophisticated methodological skills including biostatistics and clinical trials design, will complement Dr. Plante's background n clinical psychiatry and sleep medicine. Training objectives will be accomplished through targeted coursework and multidisciplinary mentorship in the context of the comprehensive scholarly resources available at the University of Wisconsin School of Medicine and Public Health. The research plan will utilize knowledge and new techniques learned to investigate novel hypotheses regarding the nature of cortical oscillations during sleep and wakefulness in depressed patients with hypersomnia, and thereby alter clinical symptomatology. Adults with unipolar major depressive disorder (MDD) and co-morbid hypersomnolence will be evaluated during sleep and wake using hdEEG, and the nature of their slow wave activity during sleep and theta/alpha activity during wake contrasted with healthy controls and MDD participants without co-morbid hypersomnia. Additionally, hypersomnolent MDD participants will undergo overnight slow wave induction, a novel neuromodulatory therapy, to both examine the role of slow waves in excessive sleepiness and evaluate the efficacy of this somatic treatment in these patients. This prospective examination of the physiologic basis of hypersomnolence in mood disorders is designed to set the stage for the applicant to develop, and ultimately test, novel diagnostic and treatment modalities among hypersomnolent mood disordered patients with the potential to meaningfully improve quality of life and illness-related outcomes. Building on didactic training and data generated by these experiments, Dr. Plante will focus the latter stages of the award on obtaining training in the design of clinical trials and developing a randomized controlled trial of the use of slow wave induction as a novel treatment for mood disorders with co-morbid hypersomnia. At the end of the award period, Dr. Plante will be well-poised to extend his research in several novel directions with clear translational relevance as a fully independent investigator in sleep and psychiatric disorders.